This application claims priority to Japanese Patent Application No. 2000-148967 filed on May 19, 2000 in Japan. The contents of the aforementioned application are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to chain saws. More particularly, the present invention relates to a chain saw which requires no separate tool for adjustment of the chain tension of the chain saw.
2. Description of the Related Art
A conventional chain saw includes a guide bar that supports the saw""s chain, with an anchor bolt and hexagonal nut provided so as to secure the guide bar to the main body of the chain saw. The chain saw is further constructed such that the guide bar is movable in the axial direction so as to allow adjustment of the chain tension. Conventionally, the process of axially moving the guide bar involves a procedure whereby a hex wrench is first used to loosen the above-mentioned hexagonal nut, a screwdriver is then inserted from the forward-facing side of the chain saw, and then the screwdriver is used to rotate an adjustment screw that causes the guide bar to move in the axial direction.
While this adjustment mechanism achieves its intended objective, it is not free from certain problems and inconveniences, thus leaving room for further improvement. For example, such a system requires the use of additional tools, namely a hex wrench and screwdriver, in order to perform adjustment of the tension of the saw""s chain. Furthermore, the necessity of inserting the screwdriver from the forward-facing side of the chain saw to adjust the chain tension presents further difficulty in performing this procedure.
In view of the above-identified problems, an important object of the present invention is to provide a chain saw with improved operability.
Another important object of the present invention is to provide a chain saw that requires no separate or additional tools for adjustment of the chain tension.
To achieve these objectives, the present invention provides a chain saw which comprises: a main body; a chain; a guide bar for supporting the chain; an anchor bolt that has an axis and is disposed within the chain saw, the anchor bolt securing the guide bar to the main body; a hexagonal nut that threadably engages the anchor bolt; a cylindrical element provided along the same axis as the hexagonal nut and adapted to be both axially movable and rotatable about the same axis as the hexagonal nut, the cylindrical element including, at one end thereof that faces the hexagonal nut, a hexagonal cavity that is adapted to engage the hexagonal nut; a lever disposed on the opposing end of the cylindrical element from the hexagonal cavity of the cylindrical element, the lever being adapted to move between a raised position and a lowered position; an adjustment pin that engages the guide bar; a screw stock that both threadably engages the adjustment pin and extends along an axis of the guide bar; a first helical gear disposed at one end of the screw stock; a second helical gear that has an axis of rotation and meshes with the first helical gear such that rotation of the second helical gear causes rotation of the first helical gear; a rotating element disposed along the same axis of rotation as that of the second helical gear, wherein rotation of the rotating element causes rotation of the second helical gear; and a sprocket cover provided on a side face of the main body, the sprocket cover defining an interior and an exterior thereof. In this chain saw, the rotating element and the lever are so arranged as to permit their operation from the exterior of the sprocket cover, and pulling the lever up to the raised position and moving the lever along the axis of the anchor bolt allows the cylindrical element to engage the hexagonal nut.
According to this chain saw, when adjusting the chain tension of the chain saw, the lever is first pulled to a raised position and then pressed toward the interior of the machine, thus causing engagement between the hexagonal cavity of the cylindrical element and the hexagonal nut. While in this position, the lever is then rotated, thus loosening the hexagonal nut. The rotating element is then rotated so as to cause rotation of the second helical gear in a desired direction. The rotation of the second helical gear also causes rotation of the first helical gear with which it is engaged. This in turn causes rotation of the screw stock, which causes the adjustment pin to travel in the axial direction of the guide bar as it is rotated. In this fashion, as the adjustment pin moves in the axial direction of the guide bar, it also causes axial movement of the guide bar. In this manner, the axial movement of the guide bar permits adjustment of the chain tension. When the adjustment of the chain tension is completed, the lever is pressed toward the interior of the chain saw, causing engagement between the hexagonal cavity of the cylindrical element and the hexagonal nut, and the lever is rotated in the direction opposite that mentioned above. This allows tightening of the hexagonal nut, thus securing the guide bar to the main body of the chain saw. In this manner, adjustment of the tension of the chain can be achieved without the use of either a hex wrench or screwdriver. Additionally, this construction greatly simplifies the process for adjusting the chain tension.
In one aspect of the present invention, the hexagonal nut, the cylindrical element, the adjustment pin, the screw stock, and the first helical gear and second helical gear are disposed in the interior of the sprocket cover such that they are integrally removable with the sprocket cover from the chain saw and attachable with the sprocket cover to the chain saw. With a chain saw so constructed, the hexagonal nut and other components are not only removed along with the sprocket cover when the sprocket cover is removed from the chain saw, but are also disposed in the sprocket cover, thus helping to prevent loss of any of the various components.
Furthermore, according to yet another aspect of the present invention, the lever is favorably constructed in a manner wherein rotation of the rotating element is at least hindered due to the rotating element being covered by the lever when the lever is in the lowered position. According to this construction, rotation of the rotating element is obstructed when the lever is in the lowered position, thus allowing prevention of unreasonable force being applied to the adjustment pin.
Furthermore, according to another aspect of the present invention, the lever is most favorably constructed such that it is provided with a structure that maintains it in the raised position as it engages the outer surface of the cylindrical element when the lever is in the raised position. This construction allows the lever to remain in the raised position, enabling the lever to be rotated with greater ease.
According to yet another aspect of the present invention, the rotating element is most favorably constructed in a manner whereby the rotating element includes at least one lug on its surface, and further wherein the lug can be grasped with the fingers when being rotated. This construction also facilitates rotation of the rotating element.
In one aspect of the present invention, the rotating element has a generally columnar shape having a top surface located substantially flush with an outer surface of the sprocket cover, and the sprocket cover includes a pair of recessed areas formed in the outer surface along the rotating element for facilitating manual rotation of the rotating element.
In another aspect of the present invention, when in the lowered position, the lever covers at least part of the rotating element and at least one of the recessed areas. According to this construction, rotation of the rotating element is obstructed when the lever is in the lowered position, thus allowing prevention of undesirable force being applied to the adjustment pin.
In yet another aspect of the present invention, the lever is attached to said opposing end of the cylindrical element so as to be pivotal between the lowered and raised positions. According to this construction, when folded in the lowered position, the lever does not hinder the use of the chain saw.
In still another aspect of the present invention, the sprocket cover includes a setting hole and the lever includes a protrusion for engaging the setting hole when the lever is in the lowered position such that engagement of the protrusion with the setting hole maintains the lever in the lowered position. This construction enables the lever to remain securely in the lowered position.
In one preferred mode, the sprocket cover includes a first rib and the lever includes a second rib adapted to engage the first rib when the lever is in the lowered position such that engagement of the two ribs maintains the lever in the lowered position.
In another preferred mode, rotation of the rotating element causes rotation of the screw stock, which causes the adjustment pin to rotate and move on the screw stock along the axis of the guide bar, thus moving the guide bar along the axis thereof.
In one aspect, when the hexagonal cavity of the cylindrical element is in engagement with the hexagonal nut, the hexagonal nut is adapted to be both loosened from the anchor bolt by manual rotation of the lever to permit axial movement of the guide bar and tightened on the anchor bolt to secure the guide bar to the main body.
In one embodiment, the present invention provide a chain saw comprising: a main body; a chain; a sprocket for transmitting rotation from the main body to the chain; a guide bar for supporting the chain; first means and second means adapted to cooperate to secure the guide bar to the main body; and a sprocket cover partially covering the sprocket, the chain, and the guide bar. In this chain saw, the first means is provided in the main body and the second means is disposed within the sprocket cover. This chain saw further comprises means for adjusting the tension of the chain disposed adjacent to the second means within the sprocket cover so as to allow both securing of the guide bar and adjustment of the tension of the chain without the use of any tool.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and descriptions which follow.